Epidemiologic studies of occupational groups are conducted to identify and clarify the role of environmental factors in the origin of cancer. Potential for heavy and prolonged exposure, coupled with the availability of work history records, make occupational groups invaluable in epidemiologic investigations of cancer. Numerous occupational groups are under investigation. Completed during the past year were studies of 1)\embalmers exposed for formaldehyde and other fixatives revealing an excess of leukemia and cancer of the brain; 2) professional artists exposed to paints and solvents, revealing high frequencies of deaths from cancers of the bladder, kidney, brain, colorectum, prostate, and breast; 3) textile workers where, unlike previous reports, the risk of prostate and colon cancer was not associated with employment in the textile industry; 4)\workers in oil refineries where a case-control study using complete work histories uncovered no striking associations between brain cancer and particular work categories; 5) pattern makers where a screening program for colorectal cancer and polps uncovered approximately a two-fold increase for cancer but no excess of polyps; 6) farmers showng chronic lymphocytic leukemia tended to be associated with cattle production while myeloid forms tended to be associated with corn, hog, and chicken production and pesticide and fertilizer use; 7) U.S. veterans where disease-specific mortality risks by occupation and industry provided clues for further research in occupational epidemiology; and 8) bladder cancer where elevated risks were noted among truck drivers that could not be attributed to smoking and other confounding factors. Other investigations under way include proportionate mortality studies of plumbers and foresters; cohort mortality studies of formaldehyde workers, anatomists, dry cleaners, furniture workers, shipyard workers, aircraft mechanics, potters, grain millers and handlers, and chemists; and case-control studies of leukemia, lymphoma, soft-tissue sarcoma, mesothelioma, and brain and lung cancer.